I'm only responsible for what I say, not for what you understand. Although as an author I am responsible for making readers understand--a reader who doesn't understand is an unhappy reader. (And there is some value to leaving some questions unanswered.
Use This Body Language Cheat Sheet to Decode Common Non-Verbal Cues - GREAT! (The attached image identifies helpful nonverbal signs that can allows us to better observe and understand what others really mean.
Imagine how much better off the world would be if we understood this: The biggest communication problem is we do not listen to understand. We listen to reply. Active listening is the most important part of active communication.